Phase-controllable growth of ultrathin 2D magnetic FeTe crystals

TL;DR

This paper demonstrates a controlled chemical vapor deposition method to synthesize ultrathin 2D FeTe crystals with tunable magnetic phases, advancing the development of 2D magnetic materials for spintronics.

Contribution

It introduces a novel CVD growth approach enabling phase control of ultrathin FeTe crystals on SiO2/Si substrates, with detailed magnetic and structural characterization.

Findings

Tetragonal FeTe is antiferromagnetic with TN ~71.8 K.

Hexagonal FeTe is ferromagnetic with TC ~220 K.

Growth temperature precisely controls the phase and morphology.

Abstract

Two-dimensional (2D) magnets with intrinsic ferromagnetic/antiferromagnetic (FM/AFM) ordering are highly desirable for future spintronics devices. However, the synthesis of 2D magnetic crystals, especially the direct growth on SiO2/Si substrate, is just in its infancy. Here, we report a chemical vapor deposition (CVD)-based rational growth approach for the synthesis of ultrathin FeTe crystals with controlled structural and magnetic phases. By precisely optimizing the growth temperature (Tgrowth), FeTe nanoplates with either layered tetragonal or non-layered hexagonal phase can be controlled with high-quality. The two controllable phases lead to square and triangular morphologies with a thickness down to 3.6 and 2.8 nm, respectively. More importantly, transport measurements reveal that tetragonal FeTe is antiferromagnetic with a Neel temperature (TN) about 71.8 K, while hexagonal FeTe is ferromagnetic with a Curie temperature (TC) around 220 K. Theoretical calculations indicate that the ferromagnetic order in hexagonal FeTe is originated from a concomitant lattice distortion and the spin-lattice coupling. This study represents a major step forward in the CVD growth of 2D magnetic materials on SiO2/Si substrates and highlights on their potential applications in the future spintronic devices.